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KVM: x86: Move CPUID.(EAX=0x12,ECX=1) mangling to __kvm_update_cpuid_runtime()

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Full equality check of CPUID data on update (kvm_cpuid_check_equal()) may
fail for SGX enabled CPUs as CPUID.(EAX=0x12,ECX=1) is currently being
mangled in kvm_vcpu_after_set_cpuid(). Move it to
__kvm_update_cpuid_runtime() and split off cpuid_get_supported_xcr0()
helper  as 'vcpu->arch.guest_supported_xcr0' update needs (logically)
to stay in kvm_vcpu_after_set_cpuid().

Cc: stable@vger.kernel.org
Fixes: feb627e8d6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220124103606.2630588-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2022-01-24 11:36:05 +01:00 committed by Paolo Bonzini
parent 1625566ec8
commit 5c89be1dd5
1 changed files with 33 additions and 21 deletions
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52
arch/x86/kvm/cpuid.c
View File

@ -196,10 +196,26 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
vcpu->arch.pv_cpuid.features = best->eax;
}
/*
* Calculate guest's supported XCR0 taking into account guest CPUID data and
* supported_xcr0 (comprised of host configuration and KVM_SUPPORTED_XCR0).
*/
static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
{
struct kvm_cpuid_entry2 *best;
best = cpuid_entry2_find(entries, nent, 0xd, 0);
if (!best)
return 0;
return (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
}
static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
int nent)
{
struct kvm_cpuid_entry2 *best;
u64 guest_supported_xcr0 = cpuid_get_supported_xcr0(entries, nent);
best = cpuid_entry2_find(entries, nent, 1, 0);
if (best) {
@ -238,6 +254,21 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
vcpu->arch.ia32_misc_enable_msr &
MSR_IA32_MISC_ENABLE_MWAIT);
}
/*
* Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
* the supported XSAVE Feature Request Mask (XFRM), i.e. the enclave's
* requested XCR0 value. The enclave's XFRM must be a subset of XCRO
* at the time of EENTER, thus adjust the allowed XFRM by the guest's
* supported XCR0. Similar to XCR0 handling, FP and SSE are forced to
* '1' even on CPUs that don't support XSAVE.
*/
best = cpuid_entry2_find(entries, nent, 0x12, 0x1);
if (best) {
best->ecx &= guest_supported_xcr0 & 0xffffffff;
best->edx &= guest_supported_xcr0 >> 32;
best->ecx |= XFEATURE_MASK_FPSSE;
}
}
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
@ -261,27 +292,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
kvm_apic_set_version(vcpu);
}
best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
if (!best)
vcpu->arch.guest_supported_xcr0 = 0;
else
vcpu->arch.guest_supported_xcr0 =
(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
/*
* Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
* the supported XSAVE Feature Request Mask (XFRM), i.e. the enclave's
* requested XCR0 value. The enclave's XFRM must be a subset of XCRO
* at the time of EENTER, thus adjust the allowed XFRM by the guest's
* supported XCR0. Similar to XCR0 handling, FP and SSE are forced to
* '1' even on CPUs that don't support XSAVE.
*/
best = kvm_find_cpuid_entry(vcpu, 0x12, 0x1);
if (best) {
best->ecx &= vcpu->arch.guest_supported_xcr0 & 0xffffffff;
best->edx &= vcpu->arch.guest_supported_xcr0 >> 32;
best->ecx |= XFEATURE_MASK_FPSSE;
}
cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
kvm_update_pv_runtime(vcpu);